Engine temperature and warm up time

Hi guys and gals, I've got a bit of a dilemma here. I've got a 2.0tdi 143. My car isn't warming to 90. It's getting to the mark half way then going up a bit when I'm going up hills, then down when going down hills. I thought thermostat so took it in to Audi a few weeks ago for warranty repair who diagnosed the stat was shagged and replaced it last Friday (warranty runs out on 17december :O). Today it's doing the same thing!

I would just take it back, if they start a repair within warranty then even if it still isn't cured by the time the warranty ends they should still honour it as the initial problem was reported within the period.

Just had it in today and basically it's "its normal for this engine temperature to fluctuate when outside temperature drops below 5deg C. This is due to the engine being so efficient. This can change due to driving style, cabin heater settings and load."

Just had it in today and basically it's "its normal for this engine temperature to fluctuate when outside temperature drops below 5deg C. This is due to the engine being so efficient. This can change due to driving style, cabin heater settings and load."

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Sounds like rubbish to me... I bet it's the temp sender unit gone faulty. This won't show a code either!

Just had it in today and basically it's "its normal for this engine temperature to fluctuate when outside temperature drops below 5deg C. This is due to the engine being so efficient. This can change due to driving style, cabin heater settings and load."

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No it is not Normal. That is bull. I have never seen that in a car unless there has been an issue with the cooling system. Is Audi different to every other car manufacturer?

If its normal then why did they do work on it in the 1st place? This sort of statement from the garage about it being normal really pi**es me off! They take us for idiots. The cooling system is designed to keep your engine temp steady at approx 90 I believe. Any fluctuation points to something within that system not working properly and at worst is the start of a major problem. The garage is speaking complete rubbish in my opinion. I stand to be corrected. Was this an Audi garage?

The 4 Audi garages near me are all pert of the same group, I called Audi uk on Friday and am awaiting a call back. Just read my manual and it says engine temp gauge should be pretty central. If engine temp is in the lower range this means the engine is not at optimum temperature. Do not accelerate hard, over rev the engine or over load the engine. Nothing about this being normal.

Just because they replaced the stat dosen't mean a thing it can still be faulty, sender can also be the cause, run the car then stop feel the hoses and that will give you an indicator of the temperature, or buy a cheap thermometer from DIY and put it on the nose this will be a rough indication of the water temperature, or stick it in the bottle make sure you have string on it...

I know that, you know that but if Audi are saying other where does that leave me? Last thing I want is the warranty to run out with a car that's gonna cost a bit if something is wrong. It ends on the 19th December and I havnt heard back from them since Thursday. They've had my car since Wednesday.

When you stat that the gauge fluctuates up and down depending on going up or downhill. Can you actually watch the needle move? If so then there is an issue on either the sensing circuit or depending on the type of system (is the temp sensor canbus?) it may be a dodgy shunt or chaffed cable). However it is definitely not 'normal' for your temp to fluctuate and any garage tech who tells you this is a liar or stupid!! Sorry to be so blunt but they are talking *hi*e!!!! And there is no such thing as a phenomenon in engine coling systems. Certainly least of all in mass produced systems like Audis. They dont know and are too scared to take responsibility. Can you please confim when the system is warm and the engine is off, what is the coolant level? When did you start to notice this? Summer/winter hot/cold etc. When does it fluctuate? You mentioned up and down hills but was the engin warm/cold etc?

The first time I noticed was in October, after a 19 mile drive on motorway the engine was still at 70deg on the dial. Then I noticed this more regular, then the fluctuating. Audi diagnosed it as a thermostat and it was booked in late nov(took 4 weeks between me reporting the fault, them diagnosing and then booking in for fix) they done the stat and it was fine as I drove 200 miles down motorway. Then after football one night it was fluctuating again on a cold engine on the motorway. So I booked it back in. That's when they came back with the internal memo about it being normal etc but they wouldn't let me keep a copy??!?! They kept it for a week and I told them to put a new temp sensor on. I got the car back today but havnt drove it yet but the tech said it made a difference.

If it was a common thing for the a4 tdi 143 temp guage to fluctuate then I'm sure I'd have another guy saying so by now.

I will monitor it over next few days then seek advice from another garage if need be.

I'd kick up a fuss mate. That Audi dealer needs a kick up the a***. You've reported it early enough (as mentioned) so they should honour it after the 19th as the problem hasn't been rectified.

Go back to the dealer and tell them to give you his personal car and you'll nail it when it's cold until your car is fixed. See how quick he takes your car in to get it fixed. Oil temperature does not fluctuate. If it does, then that's what the fan is for to cool it down. There will be more wear on the engine if you're constantly driving it around with it not running at the optimum temperature - when the engine goes bang you will be more likely to kick up a fuss so do it now to save you the hassle down the line.

Mate. Even a visit to a friendly local garage would help. Ask the question, tell them what you have been told and ask for their opinion. Cant do any harm and shouldnt cost more than a pack of biscuits for tea break.

I notice that someone mentioned oil temp. I believe the temp is coolant temp?

Drove it today after getting it back on Friday. Outside temp 8deg C drove about 15 mile on motorway engine still never warmed. Popped bonnet, top rad hose was stone cold and water was squirting back into the bottle from the little pipe on the top. Is that normal??

Sorry to hear you still have issues.
VERY unlikely your head gasket is the issue as you have no water loss, blowing water out from the expansion bottle or external water leaks.
Yes water going back to the expansion bottle is normal when running as this is to protect the engine cooling system and allow flow.
The top hose should have been warm to hot after 15 minutes of driving, again this still points to thermostate, if you get no joy from the dealer, inform him you will take it to an indepent workshop for repair and full report will be handed back to the dealership regarding the costs.
Do you have a VW dealer close by get them to do the job.

Without going into fine detail of the location it is generally at the end of the radiator hose at the engine.
There are two types of cooling system outlet regulated and inlet regulated, both systems have a bypass to WARM the engine then the stat will open to cool the engine down.
Looking at a cooling circuit the system is inlet controlled hence the cooled water returns to the engine, if the stat is stuck open it will ALWAYS run cold.
The cooling system is spec'd to run without the fans and then the fans will come on during no or slow forward movement, the stat can be removed and checked for operation in a sauce pan then heat the water up and see the temperature it opens at, these new stats are designed to fail open.
1 - Connector
2 - Coolant hose, upper
3 - To heater core
4 - From heater core
5 - To connector in coolant hose, upper
6 - Engine Coolant Temperature (ECT) Sensor (G62) Blue in color
7 - Bracket
8 - O-ring
9 - Connector (Always replace)
10 - Bolt: 10 Nm (7 ft lb)
11 - Coolant line
12 - To radiator, upper part
13 - O-ring (Always replace)
14 - To expansion tank, lower part
15 - Bolt - 15 Nm (11 ft lb)
16 - From radiator, lower part
17 - Coolant thermostat
18 - Oil cooler
19 - Coolant or Water-pump
20 - Cooler For EGR
21 - To expansion tank, upper

My current A4 the fan does not come on after stopped (2006, 2.0 TDI) my Q5 the fan will come on when stopped (2012 2.0 TDI), the reason behind this, the car cooling water will generate more temperature when stopped as no flow (terminology is after boil) hence the fan running to cool the water down.
Can you check the temperature of the water in the water bottle after the car has been running this will give you the best guide to the temperature against your in-car gauge.

The Audi dealership will have to repair this as still covered by the warranty, this is a total loss to them!!
The car has to operate correctly which includes the cooling system, if they charge you for the repair make sure you get the old thermostat in your hand, also the warranty will be for 1 year after the repair.
There are other threads on other forums which shows how this can be done if you are mechanically minded takes about 30 minutes and 25 pounds for parts, remember to catch the coolant.
I hope you get this sorted soon, I will be heading home tomorrow arrive Thursday I can then give you a full temperature report for my A4.

I've just been to a Audi specialist garage who put this blue test kit to test for gases in the expansion bottle.
If the colour was to change green that would defo indicate combustion gases in the coolent but if nothing it wouldn't change at all.
It changed a really light blue turquoise colour.

Also on my way home I had a fiddle about. When I turned the heaters off the engine temp went to 90. When I turned them on it dropped to 70. This c rules out the fact about the outside temp being below 5deg C as it was at 9deg C.

They also said the engine should reach 90 then stay there. The fault could be -
Coolant pump
Thermostat
Sender unit
Head gasket.

I have only ever tested a cooling system with paper for the PH of the water, thats a new one on me!!

I have done a bubble test on cooling systems for head gaskets many times.
Coolant pump- that would leak or cause overheating not over cooling
Thermostat- not operating correctly, partially open will give the symptoms you are seeing, as you have reduced the water around the heater and the engine can control what is going on, open heater bigger water flow the stat cannot cope.
Sender unit- as all electronics can fail
Head gasket- no water loss, oil still black, oil level not rising as the water properties of the oil are good, no over pressure in the cooling system.

Back to the thermostat, new means nothing, there are higher failure in new parts than aged parts. The terminoligy we use is infant mortality, ( the younger the part, the greater chance of the failure).
Again never heard on anyone checking combustion gasses in water with litmus paper

I'd say that it was the thermostat to be honest. I had one go on my Civic once and had almost exactly the same symptoms. Temperature held at 70 degrees unless you thrashed it and even then the heater basically didn't heat at all...

I'd say that it was the thermostat to be honest. I had one go on my Civic once and had almost exactly the same symptoms. Temperature held at 70 degrees unless you thrashed it and even then the heater basically didn't heat at all...

I've just been to a Audi specialist garage who put this blue test kit to test for gases in the expansion bottle.
If the colour was to change green that would defo indicate combustion gases in the coolent but if nothing it wouldn't change at all.
It changed a really light blue turquoise colour.

Also on my way home I had a fiddle about. When I turned the heaters off the engine temp went to 90. When I turned them on it dropped to 70. This c rules out the fact about the outside temp being below 5deg C as it was at 9deg C.

They also said the engine should reach 90 then stay there. The fault could be -
Coolant pump
Thermostat
Sender unit
Head gasket.

Now what?

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There is something amiss here. None of what you state suggests anything other than a thermostat. Assuming that its a standard mechanical stat. You can remove it. It will be closed. Drop it into a pan of boiling water and it will open. How long does the car take to heat up? If its a lonf time then i would agree with stuck open stat.

Get an AA report and then go with that in hand to the garage then when they fix it claim the money for the report back.. Contact

With the engine temp now being related totally to the heaters it can only be the stat. But they say they've changed it ???? It's booked in for the 27th so see what happens then.

My mpg has gone down to 39 and after a long run on motorway yesterday the temp reached 90 on the dash only to go back down as and when I increased the blower temp. Strange but it seems the engine can't keep it's temperature......I might put some calpol in the tank ha!!

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